Haze Review

Review of Regional Haze Situation for April 2020

1.1 Northeast Monsoon conditions prevailed over most parts of the ASEAN region in April 2020. The prevailing winds blew mainly from the east or southeast over the eastern half of the Mekong sub-region, and from the southeast or south in the western half of the sub-region. In early April 2020, there was a gradual increase in shower activities over the eastern half of the sub-region. By the latter half of the month, an increase in shower activities were also observed over the western half of the sub-region. In the southern ASEAN region, scattered showers fell over most parts of the region. The prevailing winds blew mainly from the northeast or east over areas north of the equator and remain light and variable in direction over areas to the south.

Figure 1: Average Daily Rainfall for Apr 2020. (Source: JAXA GsMaP)

1.2 In April 2020, hotspot activities continued to remain elevated in the Mekong sub-region, but the overall hotspot count was lower compared to that of past years. In the southern ASEAN region, the hotspot activities continued to remain subdued.

Figure 2: Hotspot count for the northern ASEAN region for Apr 2013 – 2020. [Note: Hotspot count from year 2019 onward is based on the NOAA-20 satellite, and for the period from year 2013-2018 is based on the Suomi-NPP satellite.]

Figure 3: Hotspot count for the southern ASEAN region for Apr 2013 – 2020. [Note: Hotspot count from year 2019 onward is based on the NOAA-20 satellite, and for the period from year 2013-2018 is based on the Suomi-NPP satellite.]

1.3 In April 2020, hotspot clusters were detected mostly in the northern Mekong sub-region, particularly in Myanmar and northern Lao PDR. These hotspot activities persisted for more than two to three weeks. Isolated hotspot activities were also detected in Cambodia and southern Lao PDR on many days. In the southern ASEAN region, isolated hotspots were detected on some days and were mostly short-lived.

Figure 4: Distribution of hotspots detected based on NOAA-20 satellite surveillance for Apr 2020.

1.4 In terms of fire intensity, the hotspot activities in northern Lao PDR, as well as in several parts of Myanmar recorded higher intensities as compared to other parts of the ASEAN region.

Figure 5: Maximum fire intensity based on NOAA-20 satellite surveillance in Apr 2020.

1.5 The smoke haze observed in the Mekong sub-region was less extensive in April 2020 as compared to March 2020. In April 2020, persistent smoke haze was observed mainly over the northern parts of the sub-region, particularly over Myanmar, northern Lao PDR, and northern and central Thailand. Over these areas, dense smoke haze was observed on many days during the first fortnight of the month, but an increase in shower activities brought a gradual improvement to the haze situation in the second half of the month. The air quality readings in northern and central Thailand improved from the Unhealthy to Very Unhealthy levels to the Excellent to Satisfactory levels by end-April 2020. Showers in the later part of the month had also brought an improvement to the haze situation in northeastern Cambodia and southern Lao PDR. In the southern ASEAN region, no significant smoke haze was observed except for localized smoke plumes emanating from some hotspots in Riau, Sumatra and the east coast of Peninsular Malaysia.

Figure 6: Number of days with moderate to dense smoke haze observed over an area based on satellite imageries, ground observations and air quality reports in Apr 2020.